1. Field of the Invention
The present invention relates to a deposition apparatus for producing an organic electroluminescence device.
2. Description of the Related Art
In an organic electroluminescence device, generally, a hole transport layer, a luminescent layer, an electron transport layer, and the like are formed as organic thin film layers between a positive electrode made of a transparent conductive film (e.g., an indium tin oxide) and a negative electrode made of a metal (e.g., Al). Holes injected from the positive electrode side and electrons injected from the negative electrode side are recombined in the luminescent layer via the hole transport layer and an electron injection layer respectively, whereby light emission is obtained.
As a method of producing an organic electroluminescence device, a vacuum deposition method is known. An organic electroluminescence material is placed in a crucible, and the temperature of the crucible and the like is raised to a vaporization temperature or higher of a deposition material in a vacuum apparatus. As a result, the deposition material vaporized from the crucible is deposited on a substrate to be a base of the organic electroluminescence device to form organic thin film layers. In order to enhance the productivity of the organic electroluminescence device, the deposition rate of a deposition material is important. If the deposition rate of the deposition material is high, the film deposition time is shortened to enhance productivity. In order to enhance the deposition rate, there may be employed a method involving bringing an opening for a deposition source close to a substrate, a method involving raising the heating temperature of a deposition material to increase the deposition rate, or the like.
However, when the opening for the deposition source is brought close to the substrate, there arise problems such as thermal influence on a mask etc. caused by radiated heat from the deposition source, and non-uniformity of the film thickness. The thermal influence on the mask causes a problem in the case of using a high-precision mask, particularly, for divisional coating of the luminescent layer. The non-uniformity of the film thickness has a large influence on the characteristics of the organic electroluminescence device, so an organic deposition film should be formed with a uniform film thickness over the film deposition face of the substrate.
Further, when the heating temperature of the deposition material is raised, there arises a problem of decomposition of the organic electroluminescence material in some cases. The decomposition of the organic electroluminescence material has a large influence on the characteristics of the organic electroluminescence device, which directly leads to the decrease in yield. As described above, in order to enhance the productivity of the organic electroluminescence device, problems such as the decomposition of the organic electroluminescence material and the thermal influence should be solved. It may be possible to increase the number of vacuum deposition apparatuses to increase the number of substrates to be processed, thereby enhancing the productivity. However, this requires a large apparatus setting area, which is not desirable in terms of investment cost.
Concerning such vacuum deposition method of the organic electroluminescence material, a method of forming a film by distributing substrates into two deposition chambers is known, for example, in Japanese Patent Application Laid-Open No. 2004-241319. According to this method, although the productivity is enhanced, the apparatus setting area increases. Thus, there is a demand for reducing the apparatus setting area and enhancing productivity.